Infusion device

ABSTRACT

An infusion device for a syringe includes a ratcheted stepper motor driven intermittently under the control of a control circuit to advance a syringe plunger driver. Different speeds are determined by the detected size of the syringe in the device. A clutch assembly disengageably connects the plunger driver to a drive belt driven by the stepper motor. 
     A connector for a tubing set has a syringe-connect portion located in a recess of the connector, and cooperates with a force sensor in the device to detect occlusions. The connector has annular projecting portions with parallel, spaced apart actuating surfaces for engagement of the force sensor in either of two positions of the connector in the device. The connector is adapted to indicate to a sensor in which position it is located.

BACKGROUND OF THE DISCLOSURE

This invention relates to devices for driving a fluid-dispensing syringeand, more particularly, to motor driven devices used in conjunction withtubing sets having specially configured connectors.

An infusion device is generally used to control the automatic dispensingof fluids from a syringe, for example, to a capillary tube which in turnmight introduce those fluids to a patient. In many cases, it isextremely important that the rate of fluid delivery be correctlyselected and accurately controlled.

In the prior art, several types of infusion devices have been used. Onetype of device incorporates a housing for supporting a syringe andutilizes an electrical motor, and associated drive circuitry configuredto drive the plunger of the syringe at a constant rate. Typically such aconfiguration incorporates a lead screw coupling between the electricmotor and the plunger. Alternatively, direct gear couplers have beenused. Stepper motors have also been used, but the power requirements forstepper motors have been greater than is desirable for a light, compactdevice.

In infusion device U.S. patent application Ser. No. 676,728, assigned tothe same assignee as the present application, a spring-driven infusiondevice is shown in which two or more substantially constant springforces can be selectively engaged to drive different capacity syringes.

It is also desirable to provide infusion devices that can accomodatedifferent size syringes and that can provide different drive rates forthe respective syringes in an automatic manner that is not dependent onoperator selection. It is furthermore desirable to provide tubing setsfor infusion devices that make the use of the devices more convenient.It is an object of the present invention to provide an improved infusiondevice with these characteristics.

Another object is to provide such an infusion device that operatesautomatically and reliably without excessive controls or controldevices, that accommodates different size syringes, and that varies thedrive rate for the syringe plunger according to the size of the syringe.

It is still another object to provide such an infusion device withimproved means for detecting occlusion and emptying of the syringe.

Another object is to provide an infusion device that will cooperate witha specially configured tubing set connector for control of the operationof the infusion device.

Still another object is to provide a tubing set connector for rapid andreliable and sterile connection to an infusion device. Another object isto provide such a connector that will cooperate with an infusion devicein determining the position of syringes in the infusion device and incontrolling the speed of operation of a syringe plunger in the deviceaccordingly.

SUMMARY OF THE INVENTION The invention comprises an infusion deviceadapted for coupling to a syringe having an elongated tubular wallextending along a tube axis with a fluid dispensing outlet port at oneend and having an internal plunger adapted for motion along the tubeaxis, comprising:

A. means for supporting the syringe wall whereby the tube axis issubstantially parallel to a reference axis associated with the device,

B. means for selectively driving the plunger over a predetermined rangeof motion along the tube axis, including:

i. a driver member for engaging the plunger,

ii. a stepper motor having an output shaft, the motor being responsiveto an applied pulse to rotate the shaft a predeterined angular incrementin a first direction,

iii. coupling means for coupling the output shaft to the driver memberwhereby the driver member translates a predetermined linear incrementalong the reference axis in response to each of the incrementalrotations of the shaft, and

iv. control means including a battery power supply and an associatedelectrical circuit means operative in a pump mode for generating asuccession of pulses, and for applying the succession of pulses to themotor, the circuit means being characterized by relatively high currentdrain from the power supply during the pulses and relatively low currentdrain from the power supply between the pulses.

In preferred embodiments the device includes a ratchet assembly coupledto the stepper motor, the ratchet assembly including means forpermitting incremental rotational motion of the shaft in the firstdirection and for preventing rotational motions of the shaft havingamplitude equal to or greater than the predetermined angular incrementin the other direction, and the ratchet assembly includes a saw-toothedrimmed disk member affixed to the armature and a ring element affixed tothe stator, the ring element including a pawl extending inward thereofand in interfering engagement with the saw-tooth rim.

Also, the coupling means of a preferred embodiment includes a firstroller and second roller, an endless belt disposed about the first andsecond rollers, motor coupling means for coupling rotory motion of theoutput shaft to the first roller, whereby the first roller rotates apredetermined angular increment and the belt translates a predeterminedlinear increment in response to each incremental rotation of the shaft,and drive coupling means for selectively coupling the belt to the drivermember.

The driver coupling means preferably includes a selectively operableclutch assembly, the clutch assembly being operative to decouple thedriver means from the belt in response to an operator applied force,said clutch assembly being inoperative otherwise. The belt in thepreferred embodiment has a ridged inner surface, the ridges extendingtransverse to the direction of the belt, and the clutch assemblyincludes a platen member overlying in a fixed relationship to the outersurface of the belt and includes a ridged clutch member wherein theridges of the clutch member are complementary to the ridges of the belt,wherein the ridged clutch member is positionable in a first positionwith the clutch member ridges engaging the ridges of the belt, andpositionable in a second position with the clutch member disengaged fromthe belt.

The invention also includes, in an infusion device including a sensorfor generating a force signal representative applied thereto in thedirection of the reference axis, control means including circuitryresponsive to the force signal for generating an occlusion alarm signalwhen the force signal is representative of a force above a predeterminedthreshold value.

In a preferred embodiment, the infusion device includes an elongatedflexible tube defining a central bore therethrough, and a rigidconnector member affixed to the tube and defining a linear central boreextending therethrough, the bores defining a continuous passageway,extending from an input port of said connector member, and the connectormember and including means for coupling the input port to the outletport of said syringe, and the connector member includes at least twosupport portions spaced apart along the axis of the connector membercentral bore and an interface portion connecting the support portions,and the outer surfaces of the support portions are substantiallyidentical in shape, the shape being adapted to interfit with the supportmember, whereby either of the support portions may be supported by thesupport member, wherein the connector member includes at least twoactuating means for selective interfering engagement with the sensor.Preferably, the actuating means includes at least two actuating surfacesfor abutting engagement with the sensor, and the actuating surfaces arespaced apart along the axis of the connector member central bore.

In another aspect of the invention, the infusion device includes sizemeans for generating a syringe size signal representative of the size ofa syringe, and the control means includes circuitry responsive to thesyringe size signal, to control the pulse repetition rate of thesuccession of pulses in a predetermined manner, the size means includingmeans for sensing the position of the fluid dispensing outlet port ofthe syringe and further comprising an elongated flexible tube defining acentral bore therethrough, and a rigid connector member affixed to thetube and defining a linear central bore extending therethrough, thebores defining a continuous passageway, extending from an input port ofthe connector member, and the connector member and including means forcoupling the input port to the outlet port of the syringe, and whereinthe connector member includes at least two support portions spaced apartalong the axis of the connector member central bore and an interfaceportion connecting the support portions, and wherein the outer surfacesof the support portions are substantially identical in shape, the shapebeing adapted to interfit with the support member, whereby either of thesupport portions may be supported by the support member, wherein theconnector member includes surface regions adapted for sensing by thesensor, each of the regions being representative of an associated one ofthe support portions being supported by the support member. The sensormay be an optical sensor, and the regions characterized by differingoptical reflectivity, or a mechanically actuated switch, and the regionscharacterized by different physical geometry, or a conductivity sensor,and the regions characterized by different electrical conductivity.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects of this invention, the various featuresthereof, as well as the invention itself may be more fully understoodfrom the following description, when read together with the accompanyingdrawings in which:

FIG. 1 shows a perspective view of an exemplary embodiment of aninfusion device in accordance with the invention;

FIG. 2 is a view like that of FIG. 1 with a hinged door of the deviceopen to show the syringe compartment of the device;

FIG. 3 is a plan view of the infusion device with the top cover removedin which one size syringe is located in the syringe compartment;

FIG. 4 is a partial plan view like FIG. 3 showing a different sizesyringe in the syringe compartment;

FIG. 5 is a sectional side view of the device along the line 5--5 ofFIG. 3;

FIG. 6 is an exploded view of the slide and the plunger driver of theinfusion device;

FIGS. 7 and 8 are views showing the relationship of the slide, plungerdriver, and drive belt for engagement of the drive belt;

FIG. 9 is a sectional view of the inside front of the device along theline 9--9 of FIG. 3;

FIG. 10 is a sectional view of the front of the device along the line10--10 of FIG. 9;

FIG. 11 is a perspective view of the connector;

FIG. 12 is a sectional view of the connector;

FIG. 13 is an exploded view of the ratchet assembly for the steppermotor of the infusion device;

FIG. 14 is a schematic diagram of the control circuit for the device forbipolar operation; and

FIG. 15 is a schematic diagram for an alternate, unipolar, operation.

DESCRIPTION OF THE PREFERRED EMBODIMENT

As shown in FIGS. 1 and 2, the infusion device 10 embodying theinvention includes an elongate housing 12 having a base member 14 and ahinged door 18 that may be opened to insert a syringe 20 and tubing set22 in a syringe compartment 24 of the device 10. The door 18 and thecover 16 are appropriately molded so that the door 18 can be snappedshut for operation of the device 10 after a syringe 20 is placed intoit.

The housing 12 also includes a front, or toe, portion 26 that defines anopen topped slot 28 when the door 18 is open. The slot 28 allowscommunication between the flexible tubing 30 of the tubing set 22 andthe syringe 20 in the syringe compartment 24.

The syringe compartment 24 extends along the length of one side of thedevice 10. Located in the syringe compartment 24 is a movable plungerdriver 32 for engagement and movement of the plunger 34 of a syringe 20placed in the compartment 24. The plunger driver 32 has a generallyplanar vertical end portion 36 perpendicular to the axis 37 of thesyringe compartment 24, including a saucer shaped shallow recess 38 inwhich the end 40 of a plunger 34 may be seated. Another portion of theplunger driver 32 is a vertical plate 42 that extends parallel to thecompartment axis 37 along a dividing wall 44 separating the syringecompartment 24 from the drive assembly compartment 46. The dividing wall44 includes a longitudinal slot 48 for connection between elements inthe syringe 24 and drive assembly 46 compartments.

The drive assembly compartment 46 (see FIGS. 3 and 5) houses near thefront portion 26 a stepper motor assembly 50 affixed to the wall 44 ofthe compartment 46. The stepper motor assembly 50 of the preferredembodiment includes a stepper motor and gear assembly unit 52 forstepping down the output of the shaft of the stepper motor 54. Anexample of such a stepper motor assembly 52 is the Airpax motor assemblysold under the model number K82237-P2 by North American Philips ControlCorp. of Cheshire, Conn. The gear ratio of the gear assembly unit 56 ofthe stepper motor assembly 52 is about 60 to 1. The output shaft 58 ofthe stepper motor assembly 52 engages a gear external 60 to the assemblythat drives a final large drive gear wheel 62 mounted for rotation on ashaft 64 affixed to a wall of the drive compartment 46, adding another 3to 1 ratio to the total gear ratio between stepper motor 54 and finaldrive gear wheel 62. On the same shaft 64 for rotation, and fixed to thegear wheel 62, is a first drive pulley wheel 66 that accordingly rotateswith the gear wheel 62. At the other, rear, end of the drive compartment46 is a second, idler, pulley wheel 68 rotatably mounted on a shaft 70fixed to the drive compartment 46. In the present embodiment the pulleywheels 66 and 68 are 1.0 inch diameter wheels, and have their axesspaced apart by 5.625 inches.

An endless drive belt 72 (see FIG. 6) is wrapped around the two pulleywheels 66,68 for translational movement in response to rotation of thefirst drive pulley 66, which, of course, rotates in response to thestepper motor 54. The belt 72 is made up of flexible material, andincludes ridges 74 on the inside surface of the belt that areperpendicular to the direction of travel 76 of the belt 72, for positiveengagement of the belt by other elements in the device.

The drive compartment 46 also includes a battery compartment 78 forholding four batteries 80 to be used as a power source for the steppermotor 54 and an electronic control circuit (described below). Suitableelectrical connections between the batteries 80, control circuit and thestepper motor 54 are made in ways known to those skilled in the art. Aprinted circuit board 82 houses the circuit for controlling operation ofthe stepper motor 54 in response to switches and sensors and is locatedin the drive compartment 46. FIGS. 14 and 15 illustrate schematicdiagrams that set forth two exemplary control circuits of the presentembodiment. In the disclosed embodiment, the stepper motor is adapted todrive the belt in a unidirection manner. The control circuit of FIG. 15provides a unipolar pulsed mode of operation, and the control circuit ofFIG. 14 provides a bipolar mode of operation. With the motor in thepresent embodiment, either control circuit may be used. In each case,the control circuit and motor configuration are pulse configurations inwhich substantially no power is drawn between pulses, permittingrelatively long operation on a set of batteries. In otherconfigurations, different control and motor arrangements may be used.

A ratchet assembly 84 (see FIG. 13), is affixed to the stepper motor 54to permit operation with minimum power consumption. In the presentconfiguration, a ratchet wheel 56 of rigid material (such as ABS) withoutwardly directed teeth 58 is affixed to the rotor of the motor 54. Aring 90 of flexible material, such as polyethylene, with an inwardlydirected, resilient pawl 92 is mounted on the housing of the motor 54 sothat the pawl 92 can engage the ratchet wheel 86 at discrete locationscorresponding to the discrete steps that the rotor of a stepper motor 54takes during operation of the motor. The ratchet ring 90 includes a setscrew 94 so that the pawl 92 can be oriented at a location correspondingto the stepper motor rotor's discrete locations. With this ratchetassembly, incremental unidirectional motion of the motor drive shaft maybe established, without requiring power drawn by the motor betweenpulses in order to maintain an established position.

The control circuit of the circuit board 82 provides a controlledoperation of the stepper motor 54. Depending on the rate of speed of theplunger 34 desired, the stepper motor 54 is pulsed with power to rotateit a discrete step, and then power to the motor from the battery sourceis effectively disconnected. For example, the motor 54 may be pulsed for10 milliseconds in a timed operation of the motor, and then power may bedisconnected for 500 milliseconds between timed operations. Thisdisconnection of the power to the stepper motor 54 conserves electricalenergy. The ratchet assembly ensures that the position of the steppermotor is maintained between pulses of power.

The drive belt 72 is selectively connected to the plunger driver 32 by aform of clutch assembly 96 (see FIG. 6). The assembly 96 includes anelongate channel member 98 affixed to the dividing wall 44 of thehousing 12. The channel member 98 includes an elongate opening 100corresponding to the opening 48 in the dividing wall 44 forcommunication between the two compartments 24,26.

A vertical slider 102 is captured between the edges 104 of the channelmember 98 for longitudinal movement along the channel member 98. Ahorizontal base pad 106 is secured to the slider 102 (in the preferredembodiment, by screws 108) and projects from the slider 102, through theslot 48, into the drive compartment 46, above and adjacent to the outersurface of the drive belt 72.

The plunger driver 32 is connected to the slider 102 by a screw 110passing horizontally through a hole 112 in the plunger drive plate 42and secured to the slider 102. The plunger driver 32 is movable, hencepivotable, about the central axis of the screw 110. A clutch pad 114extends horizontally from the plunger driver plate 42, through anopening 115 in the slider 102, into the drive compartment 46, beneaththe drive belt 72. The clutch pad 114 has located on its upper surface(beneath the belt) a set of parallel ridges 116 corresponding to theparallel ridges 74 of the belt 72 for effective engagement therewith.

A coil spring 118 is captured between a recess 120 in the bottom of theclutch pad 114 and a recess 122 in the slider 102. The spring biases 118the clutch pad 114 of the plunger driver 32 upwardly against the belt 72so that the belt 72 is captured between the clutch pad 114 and the basepad 106 for firm engagement of the plunger driver 32 with the belt 72(see FIG. 7).

The plunger driver 32 includes a horizontal upper lever tab 124positioned above the spring 118 so that downward pressure on the tab 124pivots the plunger driver plate 42 (and clutch pad 114) downwardlyagainst the bias of the spring 118, and moves the clutch pad 114 fromengagement with the belt 72 (see FIG. 8). The plunger driver 32 andslider 102 can then be moved longitudinally, as a unit, independently ofthe belt 72. This is done to position the plunger driver 32 in thesyringe compartment 24 before operation of the infusion device 10.

In the preferred embodiment the infusion device 10 is used incooperation with a tubing set 22 having a connector 126 like that shownin FIGS. 11 and 12 coupled to an elongated flexible tube. The connector126 is a tubular plastic element 128 having a central bore 130 with anaxis 132 into which is embedded at one end the elongated flexible tubing30 for intravenous use. The tubing 30 has a central passageway 134 forthe passage of fluid from the syringe 20 through the tubing 30. It iscoupled to the connector member 126 so that the central bore 130 of theconnector 126 communicates with the central passageway 134 of the tubing30. In the preferred embodiment, the tubing is polyvinyl chloride 85-90durometer with a microbore interior diameter (less than 0.020") and athick wall.

As shown in FIGS. 11 and 12 the end of the connector 126 opposite thetubing 30 includes a syringe-connect portion 136 for mounting theconnector member 126 on the outlet end portion 138 of a syringe 20. Theconnector member 126 defines a recess 140 within which thesyringe-connect portion 136 is located. The syringe-connect portion 136includes a substantially cylindrical projection 142 having an innercentral bore 144 communicating with the connector bore 130. The connectportion's inner bore 144 is adapted to receive the nozzle 146 of asyringe end portion 138 in a tightly fitting engagement. The outersurface 148 of the cylindrical projection 142 is tapered outwardly andrearwardly in a luer taper to engage, if necessary, a correspondingsurface 150 on the syringe 30. It is not necessary to threadedly securethe connector 126 to the syringe 20 because, as will be seen later, thepositioning of the connector 126 in the infusion device 10 prevents itsdisengagement from the syringe 20.

With the connector 126 mounted on a syringe 20, the syringe 20 may beinserted into the syringe compartment 24 of the infusion device 10. Thesyringe compartment 24 includes a syringe support plate 152 having aconcave upper surface 154 corresponding generally to the cylindricalsurface of the syringes resting thereon. The support plate 152 includesa number of parallel grooves 156 for seating the flanges 158 of syringes20 of different sizes. The grooves 156 are wide enough to permit somelongitudinal movement of the syringes 20, particularly to allow enoughmovement to affect a force sensor assembly, to be described below. Thegrooves 156 are marked to indicate the size of the syringe 20 to whichthey correspond.

The position of the connector 126 in the infusion device 10 isdetermined by the size of the syringe 20. For smaller syringes (e.g.,those of 10 cc and 20 cc capacity), the entire connector 126 will beinside the infusion device, and only the flexible tubing 30 will extendthrough the slot 28 at the front of the device 10 (see FIG. 4). Forlarger and longer syringes (e.g., those of 30 cc capacity), a portion ofthe connector 126 will extend through the slot 28 (see FIG. 3).Accordingly, the starting point for the plunger driver 32 will beapproximately the same regardless of the size of the syringe 20.Furthermore, detection of the position of the connector 126 in theinfusion device 10 will determine whether small or large syringes are inthe device. In some cases, smaller syringes may be emptied at higherspeeds than larger syringes, with the position of the connector beingused to control the speed of the drive motor assembly 52, as will beseen below.

If a smaller syringe 20 is used, the proximal, annular surface 160 ofthe connector 126 (the surface closest to the tubing 30) will abut aforce sensor assembly 162 located just inside the front, or toe, portion26 of the device housing 12. The force sensor assembly 162 comprises ametal U-shaped plate 164 with a surface 160 engaged by the actuatingannular surface of the connector 126.

The sensor plate 164 is pivotally secured to the housing 12 to pivotabout an axis 168 perpendicular to the axis 37 of the syringecompartment 24. The sensor plate 164 includes a surface 170 extending tomeet a contact plate 172, against which it is pivotally biased by aspring 174 on a screw 176 passing through a hole 178 in the sensor plate164. As long as fluid is proceeding without occlusion out of the syringe20 under action of the plunger 34, the sensor plate 164 does not moveaway from contact with the contact plate 172 against the biasing forceof the spring 174. If there is an occlusion, or if the end of theplunger travel has been reached, the force that results will betransmitted to the syringe 20 and connector 126 and then by theconnector actuating surface 160 to the sensor plate 64. The force of thespring 164 is calibrated so that this larger force will cause the sensorplate 164 to pivot and break contact between the sensor plate 164 andcontact plate 172, sending an appropriate signal to the control circuit82 to actuate an alarm, or shut off the motor.

The connector 126 is arranged so that it has two parallel surfaces160,180, spaced apart along the axis of the connector 126, for actuatingthe force sensor 162, depending on where the connector 126 is located inrelation to the infusion device 10. If a small syringe is used in theinfusion device 10 (see FIG. 4), the connector 126 will be locatedentirely inside the infusion device 10, and the front actuating annularsurface 160 of the connector 126 will be in abutting engagement with thesensor plate 164. If a large syringe is used (see FIG. 3), themidsection 182 of the connector 126 will occupy the slot 28, and therear actuating annular surface 180, parallel to the front actuatingsurface 160, will engage the force sensor plate 164. The connector 126thus forms a "dumbbell" shape, with outwardly extending annular portions184 at either end to form the actuating surfaces 160,180.

The infusion device 10 is arranged to provide different rates of plungertravel depending on size of the syringe 20 in the syringe compartment24. The position of the connector 126 relative to the front of theinfusion device 10 is the basis in the embodiment for determining whichrate of speed should be used. The infusion device 10 in the embodimentincludes a microswitch assembly 186, including an arm or plate 188intruding into the toe portion 26 of the syringe compartment 24 wherethe connector member 126 is located during operation of the device 10.The microswitch arm 188 will occupy one position when the intermediatemidsection, or interface, portion 182 of the connector 126 is contactedby it, and another position when an outwardly extending annular portion184 of the connector is contacted. The different positions aretranslated by the control circuitry into different speeds of theoperation of the driver stepper motor 54. The speed is doubled, forexample, by allowing only 250 milliseconds between pulsed operations ofthe stepper motor 54, rather than 500 milliseconds, as described above.A second mircoswitch assembly, not shown, may be included to sensewhether a syringe 20 is in the compartment at all.

An alternative embodiment is to have an optical sensor sensing a surfaceof the connector 126. The connector, in those circumstances, would havedifferent surface textures or different optically reflecting properties,at axially spaced apart locations on the connector, so that thedifferent characteristics sensed would indicate which size syringe is inthe infusion device. The unipolar circuit of FIG. 15 includes positionsensor (denoted x) which may be positioned near the toe of the syringecompartment to provide this optical sensing operation. In yet otherembodiments, a sensor may be used which detects the electricalconductivity of certain regions of the connector 126, with theconductivity of those regions being different so that the position ofconnector 126 along the reference axis may be determined.

In operation, the tubing set 22, which includes the flexible tubing 30to carry the fluid from the infusion device 10, is coupled to a syringe20 by mounting the syringe-connect portion 136 on the syringe outlet endportion 138. Because the syringe-connect portion 136 is recessed in theconnector 126 (the outer edge 192 of the syringe-connect portion 136 issubstantially at, or inward of, a plane (represented by the dashed line194 in FIG. 12) defined by the end face 196 of the connector 126) thetubing 30 may be coupled to a syringe 20 with a minimum risk that thesyringe-connect portion will be contacted by non-sterile surfaces,particularly, for example, the hands of personnel making theconnections.

The syringe 20 is then placed in the syringe compartment 24, at aposition corresponding to its size. The grooves 156 in the syringesupport plate 152 may be used to locate the syringe. The connector 126is also a guide. For smaller syringes it is placed entirely in thedevice housing 12; for larger ones, the connector is inserted in theslot 28. An indication of where the connector 126 is to be placed isgiven by the position of the plunger driver 32. It occupies almost thesame starting position for all size syringes, requiring that theconnector 126 be inside for small syringes and partially outside forlarge syringes.

The door 18 to the syringe compartment 24 may then be closed. A switch,not shown, may then be turned on to begin operation of the device 10.Upon actuation (see the circuit diagram of FIG. 14), the stepper motor54 will be operated by the control means 82 of the device 10 to turn onfor approximately 10 milliseconds, and advance a step. When it advances,the drive belt 72 does too (at about a 200 to 1 gear ratio), and so doesthe plunger driver 32. Then the power to the stepper motor 54 isdisconnected by the control circuit 82, to conserve electrical energy.The ratchet assembly 84 assures that the advance of the stepper motor 54is maintained during this period of shut-down of the motor, and that themotor shaft is in the correct position for the next advance.

If the control circuit 82 detects a smaller syringe in the housing 12,because of a signal from the microswitch assembly 186, it willre-energize the stepper motor 54 after a period of 250 milliseconds.This corresponds to a plunger driver speed that will empty a 10 cc or a20 cc syringe in about a half-hour. If the control circuit 82 isinformed by the microswitch 186 that a larger syringe is in place, theperiods of shut-down will be longer (e.g. 500 milliseconds), and theplunger driver speed will be slower. By way of illustration, a 30 ccsyringe would be emptied in about an hour.

If an occlusion occurs, or when the plunger reaches the end of itstravel, the control circuit 82 will react to a signal from the forcesensor assembly 162 to energize an alarm, such as a light or buzzer,and, if desired, shut off the motor.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiment is therefore to be considered in all respects as illustrativeand not restrictive, the scope of the invention being indicated by theappended claims rather than by the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are therefore intended to be embraced therein.

What is claimed is:
 1. An infusion device adapted for coupling to asyringe having an elongated tubular wall extending along a tube axiswith a fluid dispensing outlet port at one end and having an internalplunger adapted for motion along said tube axis, comprising:A. means forsupporting said syringe wall whereby said tube axis is substantiallyparallel to a reference axis associated with said device, B. means forselectively driving said plunger over a predetermined range of motionalong said tube axis, including:i. driver member for engaging saidplunger, ii. stepper motor having an output shaft, said motor beingresponsive to an applied pulse to rotate said shaft a predeterminedangular increment in a first direction, iii. coupling means for couplingsaid output shaft to said driver member whereby said driver membertranslates a predetermined linear increment along said reference axis inresponse to each of said incremental rotations of said shaft, and iv.control means including a battery power supply and an associatedelectrical circuit means operative in a pump mode for generating asuccession of said pulses, and for applying said succession of pulses tosaid motor, said circuit means being characterized by relatively highcurrent drain from said power supply during said pulses and relativelylow current drain from said power supply between said pulses, whereinsaid coupling means includes:i. a first roller and second roller, ii. anendless belt disposed about said first and second rollers, iii. motorcoupler means for coupling rotory motion of said output shaft to saidfirst roller, whereby said first roller rotates a predetermined angularincrement and said belt translates a predetermined linear increment inresponse to each of said incremental rotations of said shaft, iv. drivecoupling means for selectively coupling said belt to said driver member.2. An infusion device according to claim 1 wherein said driver couplingmeans includes a selectively operable clutch assembly, said clutchassembly being operative to decouple said driver means from said belt inresponse to an operator applied force, said clutch assembly beinginoperative and said driver means being coupled to said belt otherwise.3. An infusion device according to claim 2 wherein said belt has aridged inner surface, said ridges extending transverse to the directionof said belt, andwherein said clutch assembly includes a platen memberoverlying in a fixed relationship to the outer surface of said belt andincludes a ridged clutch member wherein the ridges of said clutch memberare complementary to the ridges of said belt, said ridged clutch memberis positionable in a first position with said clutch member ridgesengaging the ridges of said belt and positionable in a second positionwith said clutch member disengaged from said belt.
 4. An infusion deviceaccording to claim 1 further comprising a sensor positioned on saidsupport means and including means for generating a force signalrepresentative of force applied thereto in the direction of saidreference axis, andwherein said control means includes circuitryresponsive to said force signal for generating an alarm signal when saidforce signal is representative of a force above a predeterminedthreshold value.
 5. An infusion device adapted for coupling to a syringehaving an elongated tubular wall extending along a tube axis with afluid dispensing outlet port at one end and having an internal plungeradapted for motion along said tube axis, comprising:A. means forsupporting said syringe wall whereby said tube axis is substantiallyparallel to a reference axis associated with said device, B. means forselectively driving said plunger over a predetermined range of motionalong said tube axis, including:i. driver member for engaging saidplunger, ii. stepper motor having an output shaft, said motor beingresponsive to an applied pulse to rotate said shaft a predeterminedangular increment in a first direction, iii. coupling means for couplingsaid output shaft to said driver member whereby said driver membertranslates a predetermined linear increment along said reference axis inresponse to each of said incremental rotations of said shaft, and iv.control means including a battery power supply and an associatedelectrical circuit means operative in a pump mode for generating asuccession of said pulses, and for applying said succession of pulses tosaid motor, said circuit means being characterized by relatively highcurrent drain from said power supply during said pulses and relativelylow current drain from said power supply between said pulses, furthercomprising a sensor positioned on said support means and including meansfor generating a force signal representative of force applied thereto inthe direction of said reference axis, andwherein said control meansincludes circuitry responsive to said force signal for generating analarm signal when said force signal is representative of a force above apredetermined threshold value.
 6. An infusion device according to claim5 further comprising:A. an elongated flexible tube defining a centralbore therethrough, and B. a rigid connector member affixed to said tubeand defining a linear central bore extending therethrough, said boresdefining a continuous passageway, extending from an input port of saidconnector member, and said connector member and including means forcoupling said input port to said outlet port of said syringe, andwhereinsaid connector member includes at least two support portions spacedapart along the axis of said connector member central bore and aninterface portion connecting said support portions, and wherein theouter surfaces of said support portions are substantially identical inshape, said shape being adapted to interfit with said support member,whereby either of said support portions may be supported by said supportmember, and wherein said connector member includes at least twoactuating means for selective interfering engagement with said sensor.7. An infusion device according to claim 6 wherein said actuating meansincludes at least two actuating surfaces for abutting engagement withsaid sensor.
 8. An infusion device according to claim 7 wherein saidactuating surfaces are spaced apart along the axis of said connectormember central bore.
 9. An infusion device adapted for coupling to asyringe having an elongated tubular wall extending along a tube axiswith a fluid dispensing outlet port at one end and having an internalplunger adapted for motion along said tube axis, comprising:A. means forsupporting said syringe wall whereby said tube axis is substantiallyparallel to a reference axis associated with said device, B. means forselectively driving said plunger over a predetermined range of motionalong said tube axis, including:i. driver member for engaging saidplunger, ii. stepper motor having an output shaft, said motor beingresponsive to an applied pulse to rotate said shaft a predeterminedangular increment in a first direction, iii. coupling means for couplingsaid output shaft to said driver member whereby said driver membertranslates a predetermined linear increment along said reference axis inresponse to each of said incremental rotations of said shaft, and iv.control means including a battery power supply and an associatedelectrical circuit means operative in a pump mode for generating asuccession of said pulses, and for applying said succession of pulses tosaid motor, said circuit means being characterized by relatively highcurrent drain from said power supply during said pulses and relativelylow current drain from said power supply between said pulses, furthercomprising:size means positioned on said support means for generating asyringe size signal representative of the size of said syringe, andwherein said control means includes circuitry responsive to said syringesize signal to control the pulse repetition rate of said succession ofpulses in a predetermined manner.
 10. An infusion device according toclaim 9 wherein said size means includes sensor means for sensing theposition of said output port of said syringe and, further comprising:A.an elongated flexible tube defining a central bore therethrough, and B.a rigid connector member affixed to said tube and defining a linearcentral bore extending therethrough, said bores defining a continuouspassageway, extending from an input port of said connector member, andsaid connector member and including means for coupling said input portto said outlet port of said syringe, andwherein said connector memberincludes at least two support portions spaced apart along the axis ofsaid connector member central bore and an interface portion connectingsaid support portions, and wherein the outer surfaces of said supportportions are substantially identical in shape, said shape being adaptedto interfit with said support member, whereby either of said supportportions may be supported by said support means, wherein said connectormember includes surface regions adapted for sensing by said sensor, eachof said regions being representative of an associated one of saidsupport portions being supported by said support means.
 11. An infusiondevice according to claim 10 wherein said sensor is an optical sensorand said regions are characterized by differing optical reflectivity.12. An infusion device according to claim 10 wherein said sensor is amechanically actuated switch and said regions are characterized bydifferent physical geometry.
 13. An infusion device according to claim10 wherein said sensor is a conductivity sensor and said regions arecharacterized by different electrical conductivity.
 14. An infusiondevice according to claim 9 further comprising a sensor positioned onsaid support means and including means for generating a force signalrepresentative of force applied thereto in the direction of saidreference axis, andwherein said control means includes circuitryresponsive to said force signal for generating an alarm signal when saidforce signal is representative of a force above a predeterminedthreshold value.
 15. An infusion device according to claims 1 or 5 or 9further comprising a ratchet assembly coupled to said stepper motor,said ratchet assembly including means for permitting incrementalrotational motion of said shaft in said first direction and forpreventing rotational motions of said shaft having amplitude equal to orgreater than said predetermined angular increment in the otherdirection.
 16. An infusion device according to claim 15 wherein saidstepper motor includes a rotatable armature and a stator, and whereinsaid ratchet assembly includes a saw-toothed rimmed disk member affixedto said armature and a ring element affixed to said stator, said ringelement including a pawl extending inward thereof and in interferingengagement with said saw-toothed rim.
 17. An infusion device adapted forcoupling to a syringe having an elongated tubular wall extending along atube axis with a fluid dispensing outlet port at one end and having aninternal plunger adapted for motion along said tube axis, comprising:A.means for supporting said syringe wall whereby said tube axis issubstantially parallel to a reference axis associated with said device,B. means for selectively driving said plunger over a predetermined rangeof motion along said tube axis, including:i. driver member for engagingsaid plunger, ii. stepper motor having an output shaft, said motor beingresponsive to an applied pulse to rotate said shaft a predeterminedangular increment in a first direction, iii. coupling means for couplingsaid output shaft to said driver member whereby said driver membertranslates a predetermined linear increment along said reference axis inresponse to each of said incremental rotations of said shaft, and iv.control means including a battery power supply and an associatedelectrical circuit means operative in a pump mode for generating asuccession of said pulses, and for applying said succession of pulses tosaid motor, said circuit means being characterized by relatively highcurrent drain from said power supply during said pulses and relativelylow current drain from said power supply between said pulses, whereinsaid syringe includes a laterally extending flange at the upstream endof said tubular wall, wherein the distance between said syringe outletport and said upstream end is a predetermined value associated with thesize of said syringe, said device further comprising: A. an elongatedflexible tube defining a central bore therethrough, and B. a rigidconnector member affixed to said tube and defining a linear central boreextending therethrough, said bores defining a continuous passageway,extending from an input port of said connector member, and saidconnector member and including means for coupling said input port tosaid outlet port of said syringe, andwherein said connector memberincludes at least two support portions spaced apart along the axis ofsaid connector member central bore and an interface portion connectingsaid support portions, and wherein the outer surfaces of said supportportions are substantially identical in shape, said shape being adaptedto interfit with said support member, whereby either of said supportportions may be supported by said support means, and wherein said meansfor supporting said syringe further includes a first support memberadapted to support one of said support portions and a second supportmember including a set of slots adapted for receiving said flange, eachof said slots being a distance along said reference axis from said firstsupport member associated with the size of said syringe.